Paediatrics · Moderate
This case is fictional and exists for study. It describes no real patient.
3 years · male
A 3-year-old boy is brought to the paediatric clinic by his mother due to concerns about his motor development. He began walking independently at 19 months. His mother notes that he falls frequently, struggles to run, and has difficulty climbing stairs compared to his playgroup peers. There is no history of trauma, recent illness, or perinatal complications. Developmental milestones in speech and social domains are age-appropriate. Physical examination reveals bilateral enlargement and firmness of the calves. When asked to stand up from sitting on the floor, he places his hands on his knees and walks his hands up his thighs to achieve an upright posture. Tone is reduced proximally in the lower limbs, and deep tendon reflexes are diminished at the knees.
Vital signs
- HR
- 105 bpm
- BP
- 98/62 mmHg
- RR
- 22/min
- Temp
- 36.8 °C
- SpO₂
- 99%
Examination findings
- Positive Gowers' sign when rising from the floor
- Bilateral calf pseudohypertrophy
- Proximal lower limb weakness
Investigations
| Serum Creatine Kinase (CK) | 14200 U/L | reference: 30-200 |
Question 1 of 3
What is the most likely diagnosis?
Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder presenting in early childhood (ages 2–5) with delayed walking, frequent falls, proximal muscle weakness leading to Gowers' sign, calf pseudohypertrophy, and extremely elevated serum creatine kinase (>10,000 U/L). Cerebral palsy presents with static neurological deficits, spasticity, hypertonia, and hyperreflexia rather than pseudohypertrophy and massive CK elevation. Spinal muscular atrophy involves lower motor neuron degeneration leading to fasciculations, severe hypotonia, and absent reflexes, with normal or mildly elevated CK. Becker muscular dystrophy is caused by mutations in the same gene but presents later in childhood or adolescence with a milder phenotype.
Teaching point: Duchenne muscular dystrophy presents in young boys with motor delay, Gowers' sign, calf pseudohypertrophy, and markedly elevated creatine kinase levels.
Question 2 of 3
Which investigation is the single most appropriate next step to confirm the diagnosis?
Genetic testing (such as multiplex ligation-dependent probe amplification or direct sequencing) for deletions or mutations in the dystrophin gene on the X chromosome is the first-line non-invasive confirmatory investigation for suspected Duchenne muscular dystrophy. Muscle biopsy was historically the gold standard but is now reserved for cases where genetic testing is negative or inconclusive. Electromyography shows myopathic changes but is invasive and non-specific. MRI of the spine evaluates spinal cord pathology, which is not indicated given the pathognomonic muscular features and huge CK elevation.
Teaching point: Genetic testing for dystrophin gene mutations is the standard first-line confirmatory test for Duchenne muscular dystrophy.
Question 3 of 3
How should the clinical finding of Gowers' sign be correctly interpreted in this patient?
Gowers' sign describes a maneuver where a patient must use their hands to 'walk' up their own legs and thighs to stand from a seated floor position. This sign specifically reflects severe weakness of the proximal lower limb muscles (pelvic girdle, hip extensors, and quadriceps), typical of primary myopathies like Duchenne muscular dystrophy. Distal weakness typically causes foot drop or steppage gait rather than Gowers' sign. Upper motor neuron lesions cause spasticity and hyperreflexia. Cerebellar ataxia causes dysmetria and broad-based gait rather than weakness-compensating postural maneuvers.
Teaching point: Gowers' sign is a classic clinical indicator of proximal lower limb muscle weakness.
Key learning points
- Duchenne muscular dystrophy is an X-linked recessive myopathy presenting in early childhood with gross motor delay, proximal muscle weakness, and calf pseudohypertrophy.
- A positive Gowers' sign indicates pelvic girdle and proximal lower extremity muscle weakness.
- First-line diagnostic confirmation for suspected Duchenne muscular dystrophy is genetic testing for dystrophin gene mutations.
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